Aircraft typically include a plurality of flight control surfaces that, when controllably positioned, guide the movement of the aircraft from one destination to another. The number and type of flight control surfaces included in an aircraft may vary, but typically include both primary flight control surfaces and secondary flight control surfaces. The primary flight control surfaces are those that are used to control aircraft movement in the pitch, yaw, and roll axes, and the secondary flight control surfaces are those that are used to influence the lift or drag (or both) of the aircraft. Although some aircraft may include additional control surfaces, the primary flight control surfaces typically include a pair of elevators, a rudder, and a pair of ailerons, and the secondary flight control surfaces typically include a plurality of flaps, slats, and spoilers.
The positions of the aircraft flight control surfaces are typically controlled using a flight control surface actuation system. The flight control surface actuation system, in response to position commands that originate from either the flight crew or an aircraft autopilot, moves the aircraft flight control surfaces to the commanded positions. In most instances, this movement is effected via actuators that are coupled to the flight control surfaces.
Typically, the position commands that originate from the flight crew are supplied via some type of input control mechanism. For example, many aircraft include two yoke and wheel type of mechanisms, one for the pilot and one for the co-pilot. Either mechanism can be used to generate desired flight control surface position commands. More recently, however, aircraft are being implemented with side stick type mechanisms. Most notably in aircraft that employ a fly-by-wire system. Similar to the traditional yoke and wheel mechanisms, it is common to include multiple side sticks in the cockpit, one for the pilot and one for the co-pilot. Most side sticks are implemented with some type of mechanism for providing force feedback (or “haptic feedback”) to the user, be it the pilot or the co-pilot. In some implementations, one or more orthogonally arranged springs are used to provide force feedback. In other implementations, one or more electric motors are used to supply the force feedback.
Although the above-described force feedback mechanisms are generally safe and reliable, each does suffer certain drawbacks. For example, the feedback mechanisms may not provide variable force feedback based on actual aircraft conditions. Moreover, the electric motor implementations are usually provided in double or triple redundant arrangements, which can increase overall system size, weight, and costs, and are usually implemented with force sensors, which also adds to system cost and complexity. Moreover, the feedback loop with force sensors and electric motors can be difficult to tune for acceptable haptic feedback because the motor is typically separated from the force sensor. This can lead to the addition of various other components and complexities.
Hence, there is a need for a pilot side stick feedback mechanism that provides variable force feedback based on actual aircraft conditions and/or that can be implemented with relatively lightweight and/or relatively inexpensive components. The present invention addresses one or more of these needs.